Corresponding samplers are already known from the state of the art. Available from Endress+Hauser for instance, are the transportable and stationary ASP-Port 2000 and ASP-Station 2000 samplers for the defined taking of samples of a fluid medium from a sample-taking site. In the know samplers, vacuum diaphragm, or membrane, pumps are used; the metering of the samples into the sample storing receptacles occurs by means of microprocessor-controlled, pneumatic components.
In the known samplers, the vacuum principle is used. The sequence control in the sample-taking works as follows: In a first step, the metering unit is pneumatically sealed-off, by the closing of a pinch valve, in order to seal the flexible, tubular line in the form of an outlet hose. The diaphragm pump then blows through the metering container to empty the suction line. This is followed by the sucking-in of fresh sample, until a defined fill level is reached in the metering container. In a third step, a selected, defined sample volume is metered; excess sample flows back to the sample-taking site. Finally, the pinch valve is re-opened, and the metered amount of sample is discharged into the sample storing receptacle.
In the case of this known technique, problems arise in certain cases in that, during the collecting of the sample, a sedimentation of the sample can occur in the metering container, which potentially can lead to a corruption of the sample.
Another sampler known from the state of the art is also available from Endress+Hauser known as the Liqui-Port 2000 sampler. The Liqui-Port 2000 sampler is a portable sampler for the fully automatic taking and distributing of samples of a fluid medium. The suction intake and metering of the sample liquid is done with a peristaltic pump. In such case, a flexible pump hose is periodically deformed by engaging rollers, whereby a pumping action is produced. For detecting the medium supplied in the tubular line, a pressure sensor is used. The sample-taking in the case of the Liqui-Port 2000 can occur at defined points in time, due to the presence of an integrated timer function. Additionally, it is possible to perform the sample-taking under quantity, or flow, control. The automatic sample distribution is accomplished by means of an automatically rotatable distributor pipe, which is positioned successively with reference to the individual storing receptacles arranged in a carousel.